Selective data deduplication

ABSTRACT

Data is selectively deduplicated such that portions of data suitable for deduplication are passed to a deduplication engine ( 1064 ) and stored in a first store ( 1072 ).

BACKGROUND

In storage technology, use of mass data storage facilities to provide data storage as a backup to mitigate the impact of data loss is well known. In order to improve storage capacity, many different deduplication techniques have been developed in which duplicated data is removed and a pointer to previously stored data is stored in its place. One deduplication technique includes inline dedupe processing in which data is passed to a dedupe process which compares data items or blocks of data (such as files or parts of files) with existing stored data to remove duplications of data before it is passed to the backup storage. Another technique includes post dedupe processing in which data items are first stored and then deduplicated after the backup is complete.

BRIEF DESCRIPTION OF DRAWINGS

For a more complete understanding of the present invention, reference is now made to the following description taken in conjunction with the accompanying drawings in which:

FIG. 1 is a schematic of data deduplication apparatus including selective deduplication;

FIG. 2 is an example of a definition file for selecting segments for deduplication; and

FIG. 3 is a flow chart illustrating the definition file of FIG. 2.

DETAILED DESCRIPTION

With reference to FIG. 1, an exemplary data deduplication apparatus 1010 comprises data processing apparatus in the form of a controller 1020 having a processor 1030 and a computer readable medium 1040 in the form of a memory. The memory 1040 can comprise, for example, RAM, such as DRAM, and/or ROM, and/or any other convenient form of fast direct access memory. The deduplication apparatus 1010 further comprises a storage facility 1070 comprising a first store 1072 and a second store 1074. The first store 1072 may provide slower access speeds than the second store 1074. The first store 1072 comprises hard disk drives, or any other convenient form of mass storage. The second store 1074 comprises a memory having random access, for example, for example, typical random access devices such as disks or other presenting a file system level abstraction and allowing random access.

The hardware of the exemplary data deduplication apparatus 1010 can, for example, be based on an industry standard server. The storage facility 1070 can be located in an enclosure together with the data processing apparatus 1010 or separately at a remote location, for example.

During use of the data deduplication apparatus 1010, the memory 1040 has stored thereon computer program instructions 1050 executable on the processor 1030, including an operating system 1062 comprising, for example, a Linux, UNIX or OS-X based operating system, Microsoft Windows operating system, or any other suitable operating system. The data deduplication apparatus 1010 also includes at least one communications interface 1080 for communicating with at least one external data source 1090, 1095, for example over a network 1085. The or each data source 1090, 1095 can comprise a computer system such as a host server or other suitable computer system, executing a storage application program 1091, for example a backup application having a backup data in a VTL file system and a storage application program 1096, for example having backup data in a Network Attached Storage (NAS) file system.

A link can be formed between the communications interface 1080 and host communications interfaces 1092, 1098 over the network 1085, for example comprising a Gigabit Ethernet LAN or any other suitable technology. The communications interface 1080 can comprise, for example, a host bus adapter (HBA) using Internet Small Computer System Interface (iSCSI) over Ethernet or Fibre Channel protocols for handling backup data in a tape data storage format, a Network Interface Card (NIC) using Network File System (NFS) or Common Internet File System (CIFS) network file system protocols for handling backup data in a NAS file system data storage format, or any other convenient type of interface.

The program instructions 1050 also include modules 1052, 1056 that, when executed by the processor 1030, respectively, provide at least two storage collection interfaces, in the form, for example, of a virtual tape library (VTL) interface 1052 and NAS interface 1054. The program instructions 1050 also include a module 1064 that, when executed by the processor 1030, provides a data deduplication engine 1064.

The exemplary virtual tape library (VTL) interface 1052 is operable to emulate at least one physical tape library, storing in a tape data storage format, for example a sequential data storage format. The VTL interface 1052 is also operable to communicate with storage facilities 1070 having existing storage applications of physical tape libraries. The exemplary Network Attached Storage (NAS) interface 1056 is operable to communicate with a data source having a Network File System (NFS) and operable to communicate with the storage facilities 1070 having existing storage applications of physical tape libraries. A Communications path can be established between a storage application 1091 of the VTL data source 1090 and the VTL interface 1052 using the interface 1092 and the network 1085. A communication path can also be established between storage application 1096 having a NAS file system and the NAS interface 1056 using the interface 1098 and the network 1085.

The VTL interface 1052 comprises a command handler 1053 for handling commands within a data stream from a data source 1092, for example commands from a Small Computer System Interface (SCSI) command set. The VTL interface 1052 may further comprises a Cyclic Redundancy Check (CRC) calculator 1054 and a buffer manager 1055 for interfacing with the deduplication engine 1064 and for reconstituting deduped data for the host computer system in response to commands. Although a CRC calculator is shown in FIG. 1, in an alternative apparatus, it may be excluded.

The NAS interface 1056 comprises a File System in User Space (FUSE) layer 1057 as described in more detail in copending U.S. Application Serial No. 12/695,261 filed Jan. 28, 2010, incorporated herein by reference in its entirety, a CRC calculator 1054 and a buffer manager 1059 for interfacing with the deduplication engine 1064 and for reconstituting deduped data for the host computer system in response to io requests. Although a CRC calculator is shown in FIG. 1, in an alternative apparatus, it may be excluded.

To backup data, the VTL interface 1052 receives a stream of data which includes data records and commands in a tape data storage format from the VTL data source 1090. The command handler 1053 actions the commands and passes the data records of the data stream to the buffer manager 1055 which interfaces with the deduplication engine 1064. The data records are passed to the deduplication engine 1064. The data records comprise a plurality of data items. A hash algorithm is run and a hash identifier calculated for each data item. The hash identifiers are compared with previously calculated hash identifiers and if a match is found, the data item for that hash identifier is considered a duplicate and can be removed. It is replaced with a pointer to the data item associated with the previously calculated matching hash identifier. It can appreciated that there may be further optimisations performed within the deduplication process that are not described here but would be known to those skilled in the art. The deduplicated data may be stored in a sequential, tape format or other known formats in the first store 1072 of the storage facility 1070.

Some data items do not deduplicate well or can not be deduplicated at all, for example due to their unique nature such as, for example, files that are very well compressed or have had some redundancy removed as part of their format. One known technique used in deduplication and data compression is content awareness. Files are first stored to disk in native form. Rules are then applied to specify which files are to be deduplicated/compressed based on age, location or file type. The type of compression or suitability for deduplication is selected based on the type of data within the stored file. The files are recursively decomposed into their elemental components until the optimal solution is determined. This operates well for data having post processed deduplication. However, it is unsuitable for inline processing, as described above, due to the delay caused by this selection process as well as the storage capacity needed to store entire files before they are deduped.

Definition files, shown for example in FIGS. 2 and 3 are loaded into the buffer manager 1055 of the VTL interface 1052 and the buffer manager 1059 of the NAS interface 1056 via web GUI upload (details not provided here). The definition files may be selectively enabled/disabled within the interfaces. The definition file depends on whether the process is in a VTL or NAS file system, step 3010, or alternatively, specific definition files may be loaded up into respective buffer managers 1052, 1059. The incoming data is then marked as being driven by a particular rule definition; and as such the buffer managers 1055, 1059 will try to match the incoming data streams against the predefined parts of the streams provided by the rule definition.

If it is determined to be a NAS source in step 3010, in step 3030, a given filetype is defined, either by magic number (first few bytes), or by filename extension. Filetype definitions are used by the NAS versions of the product. A VTL has no means of identifying files and sees tape ‘records’, whereas the NAS protocol sees ‘files and file requests’. If it is determined to be of a file type not suitable for deduplication in step 3030, i.e. not one of a predetermined type, the file is sent to the second store 1074, step 3150.

If it is determined to be a file type suitable for deduplication, the given stream is then defined in terms of its constituent bytes/entities and decomposed into segments to determine whether to send the segments to dedupe. This is determined by steps 3050 to 3110. This is carried out per streamtype, or multiple stream types per definition may be uploaded.

In step 3050, a headertype, is tagged with either the bytes it starts and ends with, or by the specification of the length, or by the specification of it ending at the next filemark (in the case of a VTL, where filemarks are present—note that a deduping NAS does not have a concept of filemarks as these are alien to the file sharing protocol, but are present on VTL in accordance with the SCSI, SSC specification). If of a predetermined headertype, step 3070 follows, if not the segment or segments are not deduped step 3190.

A number of record types then follow, these define a (possible) given length and the bytes it starts with to be matched, and whether it will go to dedupe, step 3070.

Multiple record type definitions may be present, and length does not have to be set in at least one case—such that there is a default record length to match against, step 3090

Lastly, the whole stream is defined in terms of composition of records, filemarks (if dealing with VTL), step 3110 catalogues and how often they occur if interspersed within the stream. Note that the marker ‘records’ within the stream definition is to show that any of the possible record types can occur as a multiple at that point in time, the corollary definition of ‘record’ means that exactly one matching record of any recordtype occurs; and equally if a recordtype of ‘anythingelse’ it would expect that record type and nothing else.

At least one of the plurality of conditions, step 3130, may then be tested for, for example further testing of obvious conditions, such as the load average on the box (overall processor load), time of day, date, current date within preset parameters, etc.

Upon the first opening and write of a file item in NAS upon the load and subsequent write of a virtual cartridge in VTL into the virtual tape device, the filetypes are checked to see if they should then be sent to dedupe for the remainder of that stream. If not, then data is sent to the second store 1074, step 3150, for the entirety of that backup session. If that check passes (including conditional checks being enforced), then the until such time as a first IO occurs to that stream it is marked as untagged by the buffer manager 1059 of the NAS interface 1056.

Once some data is attempted to be written to a backed up data item (either NAS file, VT cartridge), then an attempt is made to match it against the stream definition—either by matching the first few bytes already written to the start of the data item (if appending to an existing item) or the incoming bytes (if rewriting from extent 0 in the item, i.e effectively writing a new item).

Upon such time as a match occurs—typically by matching the defined bytes tagged beside the stream type definition, then the buffer managers 1055, 1059 process checks every record it sees according to the format defined in the stream type steps 3050 to 3110. If it at any point the process loses track of where it is, it will try and resynchronise on the nearest fixed location boundary—e.g. a fixed length record, in the case where IO sizes match this (obvious for VTL due to tape record length) these are attempted to be matched against. In the case of a NAS file IO, then the stream is decomposed into segments of integral amounts of the defined record sizes.

When a given record is noted as matching, then the condition is tested, step 3130, such as specific environmental data or times of day to further specify whether data should go to dedupe, step 3170, or not step 3190. Once at least one of conditions have been met, step 3130, or not, then a given portion or segment of data can be sent to dedupe, step 3170, or in the case of NAS to the second store, step 3150. Therefore data is sent to the most applicable place.

The segments may comprise at least one chunk of data. To simplify the processing requirements, the chunk may comprise a 64 KB bucket of data that are either in dedupe or resident on disk.

On readback, for example, data is then retrieved from either of the first or second stores 1072, 1074 and reconstituted appropriately (and, thereafter, CRCs calculated by the CRC calculators 1054, 1058 as appropriate before returning data out through the relevant protocol stacks—either SCSI over iSCSI/Fibre Channel (FC) or file requests CIFS/NFS.

As a result determining the type of data before dedupe enable data to be sent to dedupe within a given stream or making it suitable for use for inline dedupe processing.

It also allows for the decomposition of streams without having to have additional processing in dedupe and allows for some specification of ‘that which does not dedupe well’ and hence allows customers to achieve higher dedupe ratios, and allows customers to not use CPU performing dedupe on data that would not dedupe.

This avoids having to manage the data at the host side to disallow the storage of certain file types that are known to dedupe badly which would limit the usefulness of the backup system. Furthermore, it avoids the application's interspersal that would otherwise hinder dedupe performance and therefore, avoids having to adjust the application defaults at the host side which is undesirable from many users' viewpoints, or to change the host application which, again, would be undesirable to the users.

Any of the features disclosed in this specification, including the accompanying claims, abstract and drawings, and/or any of the steps of any method or process so disclosed, may be combined in any combination, except combinations were the sum of such features and/or steps are mutually exclusive. Each feature disclosed in this specification, including the accompanying claims, abstract and drawings may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of any foregoing embodiment. The claims should be construed to cover merely the foregoing embodiment, but also any embodiments which fall within the scope of the claims which will be readily apparent to the ordinarily skilled person reading the foregoing. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification, including the accompanying claims, abstract and drawings, or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

The embodiment within the scope of the present invention also includes at least one computer readable medium for having above described computer executable program instructions or data structures stored thereon, also known as computer software. Such computer readable medium can be any suitable medium accessible by a general purpose or special purpose computer system or data storage system. Computer executable instructions may comprise, for example, instructions and data which cause a general purpose computer, special purpose computer, or other special purpose processing device to perform a certain function or group of functions. The software of the present invention can be implemented in several different ways. The implementation of software is not limiting on the invention. 

1. A method of selectively deduplicating an incoming data stream, the method comprising: using a deduplication engine to deduplicate selected segments of an incoming data stream, each segment being defined in accordance with a predetermined type and selected according to its defined type for deduplication; and within a first store, storing the deduped data segments.
 2. The method of claim 1, wherein the method further comprises selecting each segment for deduplication if at least one predetermined condition is met.
 3. The method of claim 1, wherein the method comprises providing a second store to store predetermined segments of data streams.
 4. The method of claim 3, wherein the method further comprises identifying the type of the source of the incoming data stream and providing a second store to store the incoming data stream of a particular type of source, not selected for deduplication.
 5. The method of claim 1, wherein each segment comprises a plurality of buckets of data.
 6. A method for selectively deduplicating data, the method comprising: uploading a plurality of rule definitions including a definition of a plurality of predetermined types suitable for deduplication into an interface; applying the plurality of rule definitions to an incoming data stream in the interface; passing data to a deduplication engine determined to be of a type suitable for deduplication.
 7. The method of claim 6, wherein the plurality of rule definitions are applied to portions of the incoming data in the interface and portions of data are passed to the deduplication engine if determined to be of a type suitable for deduplication.
 8. The method of claim 6, wherein the data comprises at least one data stream and the plurality of rule definitions are applied to each of the at least one data stream.
 9. A method according to claim 6, wherein the plurality of rule definitions include at least one predetermined condition and if at least one condition is met the pre-processed data is passed to the deduplication engine.
 10. Apparatus for selectively deduplicating an incoming data stream, the apparatus comprising: a deduplication engine for deduplicating selected segments of an incoming data stream, each segment being defined in accordance with a predetermined type and selected according to its defined type for deduplication; and a first store for storing deduplicated data.
 11. The apparatus of claim 10, wherein the apparatus further comprises at least one interface operative to receive incoming data streams from at least one host computer system.
 12. The apparatus according to claim 11, wherein the apparatus further comprises a second store for storing incoming data stream from a particular type of file system of the at least one host computer system.
 13. Apparatus for selectively deduplicating data, the apparatus comprising: at least one interface operable to receive and upload a plurality of rule definitions including a definition of a plurality of predetermined types suitable for deduplication to receive incoming data and to apply the plurality of rule definitions to the received data; and a deduplication engine operable to receive the data determined to be of a type suitable for deduplication.
 14. The apparatus of claim 13, wherein the plurality of rule definitions are applied to portions of the incoming data in the interface and portions of data are passed to the deduplication engine that are determined to be of a type suitable for deduplication.
 15. The apparatus of claim 13, wherein the data comprises at least one data stream and the plurality of rule definitions are applied to each of the at least one data stream.
 16. The apparatus of claim 13, wherein the plurality of rule definitions include at least one predetermined condition and if at least one condition is met the pre-processed data is passed to the deduplication engine.
 17. A computer readable medium having stored thereon computer program instructions that, when executed by a processor, cause a computer system to: segment an incoming data stream; define the type of each segment according to a predetermined type; select segments in accordance with their type; and deduplicate the selected segments.
 18. The computer readable medium of claim 17, wherein the computer program instructions that, when executed by a processor, cause a computer system to: select each segment for deduplication if at least one predetermined condition is met.
 19. A computer readable medium having stored thereon computer program instructions that, when executed by a processor, cause a computer system to: upload a plurality of rule definitions including a definition of a plurality of predetermined types suitable for deduplication into an interface; apply the plurality of rule definitions to data in the interface; and pass data to the deduplication engine if determined of a type suitable for deduplication.
 20. The computer readable medium of claim 19, wherein the computer program instructions that, when executed by a processor, cause a computer system to: apply the plurality of rule definitions to portions of the data in the interface and portions of data are passed to a deduplication engine if determined to be of a type suitable for deduplication. 